Comparison of two bioelectrical impedance analysis models for total body water measurement in children

We compared two bioelectrical impedance analysis models, the right-sided tetrapolar method and an experimental cylindrical method, to total body water (TBW) determined by isotopic dilution in 37 prepubertal children aged 5–9 years, who were divided into development and cross-validation groups. Despite its theoretical advantage, no improvement in predicted TBW was seen with the experimental method. The best predictive equation, using the tetrapolar method, was TBW (kg) = 1·84 + 0·45 (height squared/resistance) + 0·11(weight); r² = 0·98; SEE = 0·62 kg.     

Comparison of two bioelectrical impedance analysis models for total body water measurement in children.

We compared two bioelectrical impedance analysis models, the right-sided tetrapolar method and an experimental cylindrical method, to total body water (TBW) determined by isotopic dilution in 37 prepubertal children aged 5-9 years, who were divided into development and cross-validation groups. Despite its theoretical advantage, no improvement in predicted TBW was seen with the experimental method. The best predictive equation, using the tetrapolar method, was TBW (kg) = 1.84 + 0.45 (height square/resistance) +0.11(weight); r2 = 0.98; SEE = 0.62 kg.     

A relationship between bioelectrical impedance and total body water in young adults

Total body water was measured using the stable isotope H2(18)O in 14 young adults. Body resistance was assessed using a tetrapolar technique using a Holtain body-composition analyzer. Total body water was highly correlated (r = 0.96; p less than 0.001) with height2/resistance. The inclusion of body weight in the prediction equation reduced the standard error of estimate from 1.9 to 1.51. Bioelectrical resistance can be used to assess other body-composition parameters such as fat-free mass and fat mass, but this use involves a number of assumptions which may confound the relationship. We suggest that the measurement of bioelectrical impedance may, however, have a role in the estimation of total body water.     

生物电阻抗分析法(BIA)测量人体成分

测量人体成分的理想方法应当是相对廉价的、病人易于接受的、可以由非专业人员来操作的、结果准确且可重复性高的。生物电阻抗分析法 ( BIA)可以部分满足这些要求。然而 ,生物电阻抗分析法 ( BIA)还有许多待解决的问题和应用的限制。本文综述 BIA的基本理论、数据分析方法。     

The prediction of total body water using bioelectrical impedance in children and adolescents

Total body water was measured in 26 children and adolescents using the stable isotope H2O18. Body resistance was measured using a tetrapolar technique with a constant 50Khz, 800 microA alternating current. Total body water was highly correlated (r = 0.97; P less than 0.001) with height2/body resistance. Measurements of body resistance are non-invasive, rapid and readily acceptable to children. For these reasons the measurement of body resistance requires further investigation, including cross validation studies and is a potentially valuable technique for assessing body composition in the paediatric population.     

Estimation of maximal oxygen uptake by bioelectrical impedance analysis

Previous non-exercise models for the prediction of maximal oxygen uptake VO(2max) have failed to accurately discriminate cardiorespiratory fitness within large cohorts. The aim of the present study was to evaluate the feasibility of a completely indirect method for predicting VO(2max) that was based on bioelectrical impedance analysis (BIA) in 66 young, healthy fit men and women. Multiple, stepwise regression analysis was used to determine the usefulness of BIA and additional covariates to estimate VO(2max) (ml min(-1)). BIA was highly correlated to VO(2max) (r = 0.914; P < 0.001) and entered the regression equation first. The inclusion of gender and a physical activity rating further improved the model which accounted for 88% of the variance in VO(2max) and resulted in a relative standard error of the estimate (SEE) of 7.2%. Substantial agreement between the methods was confirmed by the fact that nearly all the differences were within +/-2 SD. Furthermore, in contrast to previously published non-exercise models, no trend of a reduction in prediction accuracy with increasing VO(2max) values was apparent. It was concluded that a non-exercise model based on BIA might be a rapid and useful technique to estimate VO(2max), when a direct test does not seem feasible. However, though the present results are useful to determine the viability of the method, further refinement of the BIA approach and its validation in a large, diverse population is needed before it can be applied to the clinical and epidemiological settings.     

Distal versus proximal electrode placement in the prediction of total body water and extracellular water from multifrequency bioelectrical impedance

In 48 normal weight subjects, 25 females and 23 males, body impedance was measured at multiple frequencies. Two different electrode placements were used, one the commonly used distal electrode placement, in which the source electrodes are on the dorsal sides of the hand and foot and the sensor electrodes are on ankle and wrist, and a second placement, in which the sensor electrodes are placed more proximally, at the knee and elbow. Theoretically a proximal electrode placement could result in more precise estimates of body water compartments. Total body water (TBW) and extracellular water (ECW) were determined using deuterium oxide dilution and bromide dilution, respectively. The aim of the study was to investigate whether proximal electrode placement results in a more precise estimation of TBW and ECW using multifrequency impedance analysis. Correlation coefficients of impedance and the impedance index stature²/impedance) with TBW and ECW were not or were only slightly higher using proximal impedance values, resulting in slight improvement of the estimation error for TBW (0.13 kg) and ECW (0.04 kg). The differences between measured and predicted values (residuals) of TBW and ECW were not correlated with TBW and ECW, but they were correlated with body fat and body water distribution (ECW/TBW). These correlations did not differ between distal and proximal impedance measurements. It is concluded that proximal impedance measurements do not substantially improve the prediction of body water compartments. © 1995 Wiley-Liss, Inc.     

The impact of equations on calculation of lean body mass by bioelectrical impedance analysis in RDT patients

Several equations are available to derive lean body mass (LBM) from bioelectrical impedance analysis (BIA). The purpose of this study was to investigate in dialysis patients the impact of the equation used on the outcome of LBM assessment. To avoid dyshydration as a confounder, vena cava diameter measurement was used to assess normohydration in the 21 patients studied. Five equations were compared. In a previously published study to assess total body water using antipyrine as a gold standard, Deurenberg's formula was advocated to be used in the estimation of LBM by BIA. Therefore, this formula was used as a basis for comparison with the other four equations. One equation gave results comparable to those obtained by Deurenberg's formula. Despite high correlations and agreement according to Bland and Altman analysis, the other three equations showed a significant difference with Deurenberg-derived LBM. Thus, the equation used has a major impact on the outcome of LBM estimations.     

A comparison of dual energy X-ray absorptiometry and bioelectrical impedance analysis to measure total and segmental body composition in healthy young adults

The aim of this study was to investigate the accuracy of BIA in the measurement of total body composition and regional fat and the fat free mass in the healthy young adults. Four hundred and three healthy young adults (167 women and 236 men) aged 18–29 years were recruited from the Mid-West region of Ireland. Multi frequency, eight-polar bioelectrical impedance analysis (BIA) and dual energy X-ray absorptiometry (DXA) were used to measure the total body and segmental (arm, leg and trunk) fat mass and the fat free mass. BIA was found to underestimate the percentage total body fat in men and women (p < 0.001). This underestimate increased in men with >24.6% body fat and women with >32% body fat (p < 0.001). Fat tissue mass in the trunk segment was overestimated by 2.1 kg (p < 0.001) in men and underestimated by 0.4 kg (p < 0.001) in women. BIA was also found to underestimate the fat free mass in the appendages by 1.0 kg (p < 0.001) in men and 0.9 kg (p < 0.001) in women. Compared to dual energy X-ray absorptiometry, bioelectrical impedance analysis underestimates the total body fat mass and overestimates fat free mass in healthy young adults. BIA should, therefore, be used with caution in the measurement of total body composition in women and men with >25% total body fat. Though statistically significant, the small difference (~ 4%) between the methods indicates that the BIA may be used interchangeably with DXA in the measurement of appendicular fat free mass in healthy young adults.     

Assessment of body composition in the prader-willi syndrome using bioelectrical impedance

The accurate assessment of body composition is of importance in the Prader-Willi syndrome. Many techniques are not applicable due to ethical or practical reasons. However, the bioelectrical impedance technique is a rapid, painless, noninvasive method of estimating total body water and hence, fat-free mass in obese children and adolescents. We have compared estimates of total body water derived from bioelectrical impedance with actual measurements taken, using H₂¹⁸O dilution, in 14 children with Prader-Willi syndrome. Existing equations for predicting total body water from impedance showed a bias to underestimate actual measures of body water. There were positive correlations between the degree of underestimation with age and body fatness. It is possible that changes in body shapes influence bioelectrical impedance measurements in obese individuals, and that a prediction equation based upon a normal population will not be applicable to obese individuals. © 1992 Wiley-Liss, Inc.     

Determination of total body water by multifrequency bio-electric impedance: development of several models

Multifrequency bio-electronic impedance analysis (MF BIA) measurements are taken from a heterogeneous group of patients, varying in size between obese and slim. The measuring system uses four electrodes: two current and two potential electrodes. Three new models are developed to calculate total body water (TBW) from the BIA data, and the resulting TBW values are compared with TBW determined by D₂O dilution. The results demonstrate that the most simple model provides the best TBW values. For individual patients, TBW can be determined by means of bioimpedance measurement with an accuracy of 3 litres. In the most simple model (model 1), the body is electrically represented by a cylinder, and corrections are made for the amount of fat. This is an extension of the model used by Xitron. In the more advanced models (2 and 3), the body is represented by a cylinder for the trunk, and truncated cones represent the arms and legs. In model 2, ΔTBW amounts to 3 litres. It is shown that the resistance of the trunk is proportional to the square root of the length. In model 3, it is assumed that subcutaneous fat is a poor conductor if electric current. An equation is developed that describes the partition of subcutaneous fat, and the fat layer is then removed from the cones representing arms and legs and from the cylinder that models the trunk.     

Estimation of extracellular space and blood volume using bioelectrical impedance measurements

Summary The bromide-82 dilution space (extracellular space, ECS) and blood volume (BV) were measured in 21 patients with esophageal and gastric cancer and in 27 patients 18–96 months after total gastrectomy. Resistance (R) and reactance (X_c) from bioelectrical impedance measurements were used to obtain multiple regression equations for ECS and BV. The variables weight, gender, and height ²/X_c were independent predictors of ECS (r = 0.767; P < 0.0001). Height 2/R and gender were predictors of blood volume (r = 0.856; P < 0.0001). The mean difference between the Br space and the ECS predicted from impedance measurements was 0 ± 1.54 (mean ± SD). The limits of agreement (± 2 SD) were therefore ±3.081 or 19.6% of the mean Br space of 15.71. The limits of agreement for BV were ±789 ml or ±19.7% of the average BV of 4008 ml. It is concluded that bioelectrical impedance plethysmography using a single frequency can be used for the estimation of ECS and BV The wide limits of agreement, however, may limit its used in clinical practice.Abbreviations ECS extracellular space - BV blood volume - R resistance - X_c reactance - SD standard deviation - LBM lean body mass - TBW total body water - RCM red blood cell mass - cAMA corrected arm muscle area - Z impedance - ANOVA analysis of variance - NS not significant - Na_e/K_c exchangeable sodium to exchangeable potassium ratio - p specific resistivity - PV plasma volume     

Assessment of body composition in the Prader-Willi syndrome using bioelectrical impedance.

The accurate assessment of body composition is of importance in the Prader-Willi syndrome. Many techniques are not applicable due to ethical or practical reasons. However, the bioelectrical impedance technique is a rapid, painless, noninvasive method of estimating total body water and hence, fat-free mass in obese children and adolescents. We have compared estimates of total body water derived from bioelectrical impedance with actual measurements taken, using H2 18O dilution, in 14 children with Prader-Willi syndrome. Existing equations for predicting total body water from impedance showed a bias to underestimate actual measures of body water. There were positive correlations between the degree of underestimation with age and body fatness. It is possible that changes in body shapes influence bioelectrical impedance measurements in obese individuals, and that a prediction equation based upon a normal population will not be applicable to obese individuals.     

Comparison of different bioelectrical impedance analyzers in the prediction of body composition

To investigate the influence of different bioelectrical impedance (BI) analyzers on the prediction of body composition from bioelectrical resistive impedance (R), 146 healthy white adults (73 men; 73 women) were studied at two independent laboratories: The University of Florida (UF) and the USDA, San Francisco. Whole body R was measured on each subject with three different BI analyzers. AT UF analyzers were: Valhalla Scientific model 1990-A (VH), RJL Systems model BIA-101 (RJL), and Medi-Fitness model 1000 (MF). At USDA analyzers were: VH, RJL, and Bioelectrical Sciences model 200Z (BES). The largest difference in R (36 ohms, P ? 0.01) was noted between BES and VH at USDA. When applied to current BI prediction equations, the observed differences among analyzers resulted in differences in predicated % fat of up to 6.3% although most comparisons among mean values (79%) showed differences below 3%. Crossvalidation of the selected BI prediction equations with hydrostatistically determines body composition using the different R values revealed total errors of prediction (E) ranging from 3.6 to 9.8% fat. The prediction equations were most accurate when used with data collected on the same instrument that was to used to develop the equation (E = 3.6 to 5.3% fat). These findings indicate that different analyzers can be a significant source of variation when predicting body composition from R. To minimize this source of variation, it is recommended that BI prediction equations be used with the same type of instrument as that with which they were developed.     

Spatial dependence of the phase in localized bioelectrical impedance analysis

The variety of phase functions, theta(z) = arctan X(z)/R(z), observed earlier on the thighs of healthy and seriously ill subjects via localized bioelectrical impedance analysis, can be represented by a model which combines realistic thigh shapes with homogeneous, axially symmetric conductivity tensors. While quantitative results depend sensitively on the way current is injected, it appears to be generally true that d theta/d(z) < 0 whenever phi(r) > phi(z) (and vice versa), where phi(r) and phi(z) are the phases of the radial and longitudinal conductivity components.     

Standardisation of bioelectrical impedance analysis for the estimation of body composition in healthy paediatric populations: a systematic review

Background: Bioelectrical impedance analysis (BIA) requires a high degree of standardisation in order to ensure valid and reproducible impedance measurements. The overall aim of this review was to study the degree to which BIA papers conducted in healthy paediatric populations (aged 0–17 years) were standardised.

Methods: Literature was identified on the basis of a systematic search of internationally-recognised electronic databases and hand searching of the reference lists of the included papers in order to identify additional relevant papers. The review was limited to lead-type BIA devices for whole-body, segmental- and focal impedance measurements. In total, 71 papers published between 1988 and 2016 were included.

To evaluate the degree of standardisation of the papers, a recently published review detailing critical factors that may impact on BIA measurements in children was used as a model for structuring and extracting data.

Results: There was a general lack of BIA standardisation, or its reporting, in the papers under review, which hinders comparison of data between studies and could potentially lead to erroneous measurements.

Conclusions: If the BIA technique should be accepted clinically for routine use in paediatric populations, there is a need for an increased focus on the importance of improved standardisation and its reporting in future studies. Consequently, this review contains recommendations for performing and reporting BIA measurements in a standardised manner.